Insulated wire joint



Nov. 18, 1952 M Q BERGAN 2,618,684

INSULATED WIRE JOINT Filed Nov. 24, 1947 26 272428 i Vr i 25 INVENTOR.

MARTIN D. BERGAN omwgatw.

ATToR'NEY Patented Nov. 18, 1952 galassi.

INSULATED WIRE JOINT Martin D. Bergan, Westfield,

The Thomas & Betts Co., Elizabeth,

N. J., assignor to N. J., a

corporation of New Jersey Application November 24, 1947, Serial N o.787,822

Claims. 1

The invention relates in general to an electrical connector, sometimeshereinafter referred to as an insul-ated wire joint, and the inventionspecifically relates to an insulated pig-tail connector for permanentlyconnecting a plurality of conductors electrically and mechanically inpermanent relation. The invention also relates to an improved techniquefor forming the connector herein featured and to a detail of the maleelement of the mold for use in forming the connector.

Pig-tail connectors as now known are formed sometimes by inserting aplurality of wire conductors, when gathered together into a bundle, intoa threaded metallic or porcelain binding sleeve and the sleeve insertedinto a preformed cap of insulating material. To secure the conductors tothe binding sleeve when made of metal it has been known to clamp theconductors between metal clamping jaws, sometimes with the clampingfaces of the jaws threaded or roughened to enhance the connectionbetween the conductors and the sleeve. The diculty present in some suchpatented devices is that the connection between the conductors andbinding sleeve is quite casual; not very positive even under the best ofconditions, and the conductors are quite apt to slip out or to be pulledout of the sleeve irrespectively as to how tight the binding action maybe, especially should a strong separating pull be imposed on theassembly of the sleeve and conductors. It has also been suggested tocrimp a cap formed of ductile metal onto the bundle of conductorsinserted into the cap and to screw or otherwise secure the cap within aninsulating member. This crimping operation for securing a metallicbinding sleeve of ductile metal onto the bundle of conductors is animprovement over the jaw clamping means above mentioned, but 4there isinvolved in this suggestion the additional step of subsequently securingthe assembly of binding sleeve and conductors to the insulating member.This latter method obviously involves additional labor in a situationwhere it is not always easy to work, and at least involves additionalexpense in forming the jointure oi complete assembly of pig-tailconnector and its cables.

It has also been suggested that an electric terminal be formed with aconductor embracing ferrule of cylindrical form over which is tted oneend of a preformed sleeve of insulating plastic material and the plasticsleeve formed of such thin cross Section of material and other wisefabricated so as to be easily distorted by a crimping operation thereonto cause the metallic errule covered thereby to bind a conductorintruded into the ferrule. While this practice has the advantage ofutilizing a single crimping operation to distort both the metallicbinding sleeve as well as its insulating plastic jacket, it likewisefails to prevent slipping between the ierrule and its insulatingcovering prior to being crimped into its final position and thus thereis no assurance that in the nal assembly the binding sleeve will beproperly located on the conductors. It has also been suggested to pressa metallic tubular sleeve into a preformed thimble or" insulatingmaterial but this develops objectionable shoulders in the bore of theconnector and shoulders in these connectors interfere with the desiredease of insertion of the conductors into place.

The primary object of the invention is to provide a simplied form ofelectric connector having the advantages oi the similar types of ductilemetallic sleeves or ferrules and insulating coverings now known, but inwhich the metallic sleeve and the insulating shell therefor can besecured together as an incident of molding the shell and in which themetal ferrule will thus be pre-Xed accurately in position in theinsulation to form an improved type of pre-insulated wire `ioint andspecifically a pre-insulated pig-tail connector.

Broadly, I attain this objective by forming the connector as a completemarketable unit formed solely of two parts, 4an insulating shell as aonepiece molded plastic unit and a metallic sleeve or ferrule lining theshell and anchored therein as an incident of molding the plastic shell,and which preformed metal lined connector may be carried in stock andcrimped on to the conductors introduced therein with a single crimpingoperation performed at the time a-nd place of USB.

Still another object of the invention is to provide an electricconnector integrally metal-lined as herein featured, and into which oneor a bundle of the conductors may be easily inserted without buckling orcurling and which inserted conductors will be automatically locatedtherein in prefixed relation to the metallic lining, binding sleeve orferrule to be crimped thereon.

The invention has for lanother objective `an improved method for moldingthe insulating shell with its lining sleeve or ferrule permanently-anchored therein in accurately prefixed relation to the balance of theshell and in which the connector so pre-lined can be formed of the leastpossible amount of material and organized to facilitate its beingcrimped into place.

Various other objects and advantages of the invention will be in partobvious from an inspection of the accompanying drawings; in part will befully set forth in the following description of one form of the pig-tailconnector; and in part will be more fully set forth in the followingparticular description of a method of molding the connector and a methodfor crimping the connector onto conductors introduced into the same, andthe invention also consists in certain new and novel modifications ofthe preferred methods and other features of construction and combinationof parts hereinafter set forth and claimed.

In the drawings:

Fig. 1 is a view in side elevation of a pig-tail connector constitutinga preferred embodiment of the invention and showing the same in itsfinal operative position in crimping engagement with the ends of apluralityof cables;

Fig. 2 is an enlarged axial sectional view showing a molding apparatusand illustrating the molding step in a method for forming the ferrulelined connector shown in Fig. l;

Fig. 3 is an end view of the open end of lthe connector shown in Figs. 1and 2 looking at the same from their right ends, before the cables areinserted therein as shown in Fig.v 1, and with the completed connectorof Fig. -2 removed from the molding apparatus;

Figs. 4 and 5 are veach axial sectional views of the molded connector ofthe preceding figures with the cables inserted therein with the Viewstaken at forty-five degrees rotation about their common axis takenrespectively on the lines d--d and 5-5 of Fig. 3, but the connector notcrimped on the conductor ends in Fig. 4, and with the connectordistorted into crimped engagement with the conductor ends;

Fig. 6 is a View in perspective of the left end of the male element ofthe molding apparatus shown in section in Fig. 2;

Fig. 7 is a transverse sectional View through the uncrimped connectortaken on the line '1 -'I of Fig. 4; and

Fig. 8 is a similar view through the crimped connector taken on the line8-8 of Fig. 5.

Referring to the finished assembly of connector and cables shown in Fig.1, there is disclosed a pre-insulated, metal lined, pig-tail connectorI0, molded to shape from a plastic insulating material and with aplurality of cables l I, herein shown tobe four, inserted into the openend of the bore I2 of the connectorras best shown in Fig. 4. Theconnector comprises two parts, an outer molded insulating shell I3 ofthe plastic material with a malleable metal sleeve or ferrule I4 liningan inner, reduced end portion of the bore I2 and equi-distantly spacedfrom opposite ends of the reduced end portion of the bore.

The cables illustrated are of conventional form and each includes a coreforming conductor I5, solid orstrandedencased in-a tube I6 of insulatingmaterial. Following conventional practices in this respect the tube ofinsulation is stripped back from the ends of the cables Il to providebared ends I'I which are closely grouped together to form a bundle andthe bundle inserted into the bore of the connector. The shell I3 is thencrimped at the sleeve lined portion thereof to distort the metal ferruleI4 onto the bundle of bare end wires I'I by opposing crimps I8 to securethe cables to the connector with their bared conductor ends mechanicallyand electrically connected permanently to each other through the ferruleI4. The ferrule I4 is formed of some ductile highly conductive metal,for instance, a dead-soft copper.

Opposite ends of the ferrule I4 are bevelled to form inwardly inclinedend faces forming an inner face I 9 and an outer face 29 in each caseforming an annular inwardly facing space adapted at each end of thesleeve to form a molding space for `the interlocks hereinafterdescribed.

It is a feature .of this disclosure that the connector I0 as marketed isformed solely of two parts; the insulating shell I3 formed of plasticmaterial and the lining tube ferrule or sleeve I4 formed of copper orlike dead conductive metal. These two parts are in interlocked relationand otherwise Yfree of any other fastening means. Neither of `these twoelements have Vany machining done on them prior to their being finallycrimped onto the bared ends I'I of the conductors. In place of the dead,soft copper suggested as preferable for use in forming the metal ferruleIll, anyother equivalent dead, soft metal may be used, for example, acopper-zinc alloy, say, about ninety per cent copper and ten percentzinc, which has been found to be satisfactory in actual practice.

Referring to Fig. 2` for a more detailed disclosure of the connector andthe manner of molding the same, there is Ydisclosed a molding devicecomprising two coacting elements, an outer female element A and an innermale element B.

lThe element A is rprovided with a molding cavity C wideopen at one endand in which is centered the `male element B as hereinafter described. Amolding space D is formed between the elements and which space isinitially vacant and herein shown to be Vlled with the plastic materialof which the shell I3 is formed.

The male element is of one-piece pin-like form and includes mainly aninner solid cylinder E of small diameter, and an outer cylinder F ofrelatively larger diameter. It is a feature of the disclosure that themidlength portion of this element B has its diameters progressivelyincreasing from the smaller cylinder E to the larger cylinder F topresent a smooth surface G of bottle neck form, and which is of a doublereverse curve, ons-shaped 'form in all axial cross sections. Along fourequidistantly spaced-apart longitudinal lines the surface G graduallyrounds without breaking from one to the other of the cylinders E and Fof different cross sections.

The outer edge portion of the enlarged cylindrical endFof the pin-likemale element B' is provided with an outstanding end flange H forming aclosure for the open end of the molding cavity C. The inner portion ofthe outstanding flange H, as it meets the perimeter of the outer end ofcylinder F is provided with a bevelled shoulder inclined at about 45degrees. The extreme outer end of the mold cavity is enlarged indiameter to form an annular rim J which defines the open end ofthefemale element A. The rim J is dened at its inner end by a stepshoulder K on which the flange H rests when tted within the rim J. Thefemale element A is provided at the end at or just beyond the placewhere the annular face I9 of the ferrule I4 is to come with a materialintake vent L leading from the outside of the mold into the moldingspace D at the closed end of the cavity. At the opposite end of the moldspace the element A is provided with a plurality of air escape vents Mfollowing usual mold practices in this respect.

It is the intent here to locate the sleeve or ferrule I4 in anaccurately preset position in the mold so that when the finally moldedconnector is removed from the mold the ferrule I4 will be set in itsintended position in the finished article and substantially centeredmidlength of the barrel 23. The prelocating of the ferrule I4necessarily means that the mold must be provided with an accuratelylocated limiting stop against which the ferrule can abut. As above notedit is also a, requirement that the funnel forming surface G be as smoothas possible. In order to obtain these two objectives a peculiar form oflimiting stop for the ferrule is provided on the male element B at thepoint where the smaller diametrical cylinder E starts to increase indiameter to form the curved surface at G. For a detailed showing of thisferrule stop reference is made to Fig. 6. The end of the small cylinderE as it enlarges to form a bottle neck is formed into a flat rectangularparallelepiped N whose sides are of equal length and equal to thediameter of the cylinder E. Cylinder E is centered in the fiat side Qfacing the cylinder E and coacts therewith to form fourcircumferentially and equidistantly spaced apart triangle faced stops R.The center of each side P is tangent to the surface of the cylinder E sothat there are four relatively wide iiow lines of uninterrupted surfacestwo of which are indicated by the long arrows in Fig. 6 across which theplastic material flows without interruption from the stop N.

In preparing the mold for use its elements A and B are separated, if notalready so, the metal ferrule I4 is inserted with a sliding t on thesmall end E of the male member and advanced thereon until its bevel face20 abuts squarely against the four exposed corner stops R. This has theeffect of iixedly locating the ferrule on the male element in thatposition which the lining ferrule is to occupy in the finishedconnector. The male element with the ferrule so threaded thereon islocated telescopically centered in the molding cavity C, with the flangeH fitted snugly within the rim J and abutting' the shoulder K. Thisinteritting of the mold elements at the outer end of the mold cavityoperates to properly locate the inner end of the male member relative tothe bottom and outlining side of the mold cavity and in this way denesthe cross section of material of the shell I3.

I'hermoplastic material O such as vinylidiene chloride or a condensationpolyamide, is introduced into the mold cavity CI through the inlet ventL following conventional practices in introducing such self -hardeningplastics into molds. The plastic material, of course, takes the formimposed thereon by the mold elements and by the pre-formed ferrule andas it fills the mold cavity gives the desired configuration to the shellI 3. By reason of the fact that the shell is molded into its iinal formthe plastic material forming the shell is free of internal strains andthis unstrained condition tends to minimize any tendency of the shell tocrack open when subjected to the subsequent crimping operation.

The connector I0 considered as a whole is closed at one end by an endwall 22 formed of the plastic O and includes a metal lined barrel 23 ofrelatively small diameter, a bottle neck shaped midportion 24, and anouter skirt or collar 25 of relatively large diameter with its boredimensioned in the instant case to receive the ends of the four cablesII with their insulation tubes I6. The bore of the mid-portion 24gradually and smoothly reduces in cross section, funnel-like, and at itspoint of minimum cross section forms a smooth annular throat forreceiving the more or less constricted bared ends II and for guiding theends so constricted smoothly into the metal-lined portion of the boreI2.

It is particularly noted that as the plastic material is forced throughthe vent L and into and along the mold cavity it moves from left toright of the showing in Fig. 2, and thus bears against the exposed leftend I9 of the metal sleeve or ferrule I4 and acts frictionally along theouter side of the same to force the advance end 20 rmly on to the fourstops R if the ferrule is not already in such place. As the plasticmaterial in effect ows to all parts of the mold cavity it eventuallyunderlaps both of the bevel faces I9 and 20 thus for-ming integralannular interlocks 26 and 2'I at opposite ends of the metal ferrule andbetween the same and the male element E to anchor the sleeve I4 to thebarrel portion 23 of the plastic shell I3. Where the outer bevel face 20of the sleeve I4 contacted the four stops R (Fig. 6) to form jointsbetween the sleeve and the parallelopiped N in the course of molding theshell, there was, of course, no plastic and thus when the connector isremoved from the mold there is exposed four points of metal each oftriangular form as shown at 20 in Fig. 3. It is noted that theinterlocks 26 and Z'I feather inwardly towards each other to a sharpedge and that their diameters at their junction with ferrule I4 is thesame as the internal diameter of the sleeve thus providing a smoothcontinuous cylindrical surface between the ends of the metal ferrule I4and the plastic shell I3. At the outer end of the skirt 25 the bevelledshoulder I forms a funnel-like opening or chamfer 28 to the open kend ofthe bore I2 to facilitate the introduction of the cables II into thebore. The entire wall surface dening the bore I2 from end to end issmooth and thus free of any shoulders or other projections from itsfunnel-like conductor intake opening 28 to its end closed by the endwall 22. The cylindrical wall defining the small diametered innerportions of bore I 2 in the portion thereof forming the barrel 23 mergesin a reentrant curved corner 29 into the end wall 22. In this way thebared cable ends are funnelled into place Without any obstruction orresistance to their insertion such as would be presented if the borewall did not have the smooth surfaced funnel shape herein featured.

The connector herein illustrated is intended to be quite small, verysmall. In the device illustrated the plastic shell I3 has a totalall-over length of of an inch; the skirt 25 is Tag of an inch long withan OD of 0.437 and an ID of 0.375; the barrel 23 is s of an inch longwith an OD of 0.281 and an ID of 0.183 and with a wall thickness of0.062 of an inch. The metal ferrule I4 is of an inch long; had an OD of0.203 of an inch; and ID of 0.183 of an inch and thus a wall thicknessof 0.024 of an inch.

AsV suggested 'inFig 4zthe bared l conductor vends l1 are usuallyhalf-twisted" into a bundleV andvthe same inserted intothe bore l2through the vopen end 2,8 of thel connector preferably with a rotatingtwist in the direction of the initial manuallyarranged lay of bared endsas the ad- Vance end of the bundle is turned somewhat as a cork insertedinto a constricted bottle neck. The conductors are inserted until theycan be no further advanced by reason of their engagement with the endwall 22. The operator then knows the wires Ifi are in their prefixedlocation to locate the ferrule Ui in proper position when the barrel 23is nallycrimped thereon.

With the bare conductor ends i? in place as shown in Fig. 4, the barrel23 and its lining sleeve or ferrule lil are distorted by squeezingtogether the opposite sides thereof to form the crimps I8 in oppositesides ofthe shell and therethrough to form the crimps 3% in the ferruleHl as shown in. Fig. 5; it is seen from Fig. 5 that the squeezingpressure forming the crimps i8 reduces the original cross-sectionaldimensions of both the stock plasticshell I3 as well as the metal liningferrule at its mid-length portion from its initial form circular incross section into a form elliptical in cross section with-the eiectthat the wires forming the ends Vi are more closely compacted, and thecrimps 3G bite into opposite sides of the wire bundle to key them to-theconnector. The device illustrated meets the requirements of theelectrical code which call for a strength of thirty pounds pull onpreformed insulators of this type and of` 2-100 volts minimum withoutvoltage breakdown of the insulating shell.

While the invention has been described specially in its application to aclosed end pig-tail connector, it is obviously within the scope of thedisclosure to provide the shell I3 of open end tubular form, that is,without the end wall 22, and thus form if desired an open end sleeveinto opposite ends of which conductors may be inserted end to endto forma splice and secured to the connector by crimping as herein disclosed.

By means of a connector as thus preformed,-

any number of cables within the capacity of the connector may be securedin interspliced electrically connecting relation. The ferrule Id in itstightening engagement with the conductor ends il welds them in intimateinter-bearing relation so that in effect thel bundle of wires at l1become a closely related strand banded together and electricallyinterconnected by the ferrule lll.

As the ferrule I4 is located in place accurately as a factoryproposition, the mechanic in the field need pay no attention to thelocating of ferrule Ill on the conductors; he simply inserts theconductors as far as they will go and forms the crimps I8 with assurancethat the wires hidden from View within the shell will be properlyconnected as intended by the manufacturer of the connector. i

I claim:

l. An article of manufacture constituting a preformed pig-tail connectorfor electrically and mechanically connecting a plurality of bared endsofY cable conductors when crimped onto the bared ends of the conductorsinserted therein, said connector formed of a hollow shell of insulatingplastic material having a bore of small diameter at one end and ofrelatively large diameter at the other end, the portion of the wall`outlining the bore in the part, thereof between the ends of large andsmall diameters rounding.

bottle-neck-like from one of said portions into theV other and providingfunnel-like surfaces for collecting and guiding the conductor ends intothe boreV of small diameter, and a long, thin, sleeve-like cylindricalferrule formed of dead soft copper embedded in the wall outlining thebore of small diameter, the bore of the metal ferrule formingv acontinuation without change of diameter or axis of the bore of theportion of the shell in which it is embedded, the material forming theplastic shell extending integrallyv in lapping relation across at least-a part of the cross section of the metal at both ends of the sleeve andadhering' thereto to anchor the sleeve plastically and permanently inplace in the shell against relative axial movement.

2. r-he connector defined in claim l and in which the metal ferrule hasat least one of its opposite ends beveled inwardly to form an internallybeveled endless ring and with the plastic material at least partiallylapping and adhering to the surfaces forming the ends of the sleeve andthus forming interlocks at opposite ends of the ferrule to secure theferrule permanently looked in the shell.

3. A connector formed of an outer shell of insulating plastic materialhaving a bore open at least at one end and a sleeve-like ferrule of softcopper forming a lining for at least a portion of the length of thebore, opposite ends of the copper ferrule being inwardly beveled, saidferrule being embedded in the plastic material and secured in placethereby against relative movement, the bore of the sleeve being flushwith the bore wall in which it isembedded, one beveled end of the metalferrule being lapped circularly by the insulating plastic material toprovide an interlock of annular form between the ferrule and shell atthis end of the ferrule, the other beveled end of the metal ferrulebeing lapped by the insulating material at a plurality ofcrcumferentially spaced-apart points, leaving said other beveled endexposed in the parts thereof between the lapped, spaced-apart points.

4.-. An insulated electric connector comprising two concentriccylindrical tubes in telescopic relation and forming a cylindrical jointtherebetween, the outer tube being formed of a molded plastic insulatingmaterial, the outer cylindrical face and at least parts of the two endsof the inner tube being embedded in the wall of the bore of the outertube and plastically secured theretoby virtue of being so embedded, saidinner tube being formed of a soft malleable metal having highconductivity, and the faces of the tubes which form the cylindricaljoint therebetween being in molded contacting relation but otherwisefree of any load across the joint.

5. An electric connector including a hollow molded shell of insulatingplastic material having a bore of small diameter at one end and ofrelatively large diameter at the other end, the portion of the walloutlining the bore in the mid-length part thereof between the ends oflarge and small diameters rounding in bottle-neck form from one of saidend portions into the other, and a sleevelike cylindrical f errule ofductile metal embedded in and plastically sealed in the wall outliningthe bore of small diameter and forming a lining for the major portion ofits length, the material forming the plastic shell forming an incompletering lapping the ferrule at the end thereof nearest the bore of largediameter, a plurality of circumferentially vs,paced-apart portions ofthe ferru-le end so lapped being exposed to view 9 through the breaks inthe incomplete ring and UNITED STATES PATENTS the bore Wall forming atS-curves in the longi- Number Name Date tudinal axial planes which liebetween the ex- 594,225 Berrdge NOV. 23, 1897 posed portions of theferrule end thereby to form 1 72g 991 at least two smooth curvedsurfaces continuously 5 2 075 558 rlgglu-"S" rounding from the bore oflarge diameter into 2122252 Hayes "June 251 193g the bore of the ferruleand free of shoulder breaks 2259261 Miner (Qtu OC@ 14 1941 for engagingthe conductors when inserted into 2261916 Meuow N0V 4 1941 the bore atits end 0f large diameter and OT 2,346,426 Haaisi; "Apr, 11j 1944guiding the Conductors alOIlg Sad S'Shaped 10 2,359,291 Franl; Feb. 13l1945 curves into the adjacent end of the ferrule bore. 429585 Rogo Oct.21 1947 MARTIN D. BERGAN.

REFERENCES CITED The following references are of record in the 15 illeof this patent:

